Elastic link straps



June 30, 1964 L. KUNZMANN 3,138,917

ELASTIC LINK STRAPS Filed April 27, 1959 I N VEN TOR.

[an/W9 K071 z mann United States Patent 3,138,917 ELASTIC LINK STRAPS Ludwig Kunzmann, Pforzheim, Germany, assignor to Rodi & Wienenberger Aktiengesellschaft, Pforzheim,

Baden, Germany Filed Apr. 27, 1959, Ser. No. 809,189 Claims priority, application Germany May 17, 1958 7 Claims. (Cl. 59-79) The present invention relates to elastic link straps for ornamental or utilitarian purposes, and more particularly to a watch strap or bracelet which consists of two superimposed layers of links which extend transversely to the longitudinal direction of the strap, and wherein the upper and lower links are staggered relative to each other and are resiliently connected with each other so as to be expansible against the action of springs which are disposed within the links.

In a copending application of David Jacobsen, Serial No. 619,339, filed on October 30, 1956, now Patent No. 2,949,729 dated August 23, 1960, there has been disclosed an elastic link strap of the above-mentioned type in which the upper and lower links consist of shell-like casings, and wherein the upper links are open in the downward direction, while the lower links are open in the upward direction and have upwardly extended side walls which project into the upper links through the bottom openings thereof. Each upper link also serves as a housing of at least one pair of curved leaf springs which engage on the one hand against the inside of the side walls of the upper links, and on the other hand against the inside of one inwardly projecting side wall of each of two adjacent lower links, so that these springs will be pressed flat when the strap is being expanded or bent. For connecting the upper and lower links with each other and for guiding them relative to each other during the expanding and contracting movements of the strap and its individual parts, the extended side walls of the lower links are provided with inwardly extending slots at the outer ends thereof and at the level of the upper edge of the low end walls of these links. The upper links are then provided with guide portions at the level of the free lower edges thereof. These guide portions of the upper links are inserted into the mentioned slots of the lower links and are guided therein for movement in the longitudinal direction of the strap. They preferably consist of extensions of the end Walls of the upper links which are bent over and inwardly toward each other so as to form short tabs which extend transversely to the upper links and in the longitudinal direction of the strap and engage in the mentioned slots in the side walls of the lower links. The side walls of the upper links are preferably notched out at each end so as to accommodate the inwardly bent tabs of these links. In my copending application Serial No. 619,198, filed on October 30, 195 6, now Patent No. 2,928,232 dated March 15, 1960, I have also disclosed that an elastic link strap of the above-mentioned type may be shortened at least at some parts thereof by providing the tablike guide portions on at least some of the upper links with a cutout at one corner and in shortening one of the tongues which are formed by the slots in the corresponding lower links so that such lower link may be unhooked from the respective upper link by passing the shortened tongue through the cutout in the tablike guide portion. The last-mentioned application also disclosed other possibilities of shortening such an elastic link strap.

Although the individual links of an elastic link strap of the type as above-described with shell-like upper and lower links of a substantially rectangular shape extending transversely of the strap and arranged closely adjacent to each other in the longitudinal direction of the strap may be made very small and narrow so that the strap will well adapt itself to the shape of a persons wrist and See has a very pleasing appearance, it also has the disadvantage that the extensibility of such a strap will decrease in accordance with the decrease of the width of the individual links. This is due to the fact that the theoretically possible extensibility is reduced by the thickness of the side walls of the lower links which extend into the upper links, further by the thickness of the material of the leaf springs between the respective side walls of the upper and lower links. Since the thickness of the side walls of the links and the thickness of the leaf springs cannot be reduced beyond a certain limit as the entire strap would otherwise be rendered too fragile, it is an unfortunate fact that the narrower the individual links of such a strap are made, as seen in their direction transverse to the length of the strap, the more the extensibility of the strap will be reduced by the total of the thickness of the side walls of all of the links and of the thickness of the material of all the leaf springs. Although a link strap of this type which is connected at both ends to a wrist watch may be extended to a length which is just sufficient to permit the strap to be slipped over the hand, it would be very desirable if the extensibility of the strap could be increased so that either of the individual links may be made still narrower or that with links of a greater width the strap may be slipped more easily over the hand.

It is therefore'the principal object of the present invention to overcome the mentioned disadvantages of an elastic link strap of the type as disclosed in my previous application and'described above and to attain a similar link strap but one of a greater extensibility in relation to the width of the individual links.

Further objects of the invention are to produce such a link strap which does not reveal any gaps between the adjacent links when the strap is in the extended position, and wherein at least some of the links are designed so as to be easily unhooked from each other to permit the total length of the strap to be easily reduced or enlarged in accordance with the size of the wrist of the person using the strap or the tension at which he wishes the strap and the wrist watch thereon to cling to his wrist.

The present invention relates to a link strap similar to that as described above consisting of two superimposed layers of links which extend in a direction transverse to the longitudinal direction of the strap, and wherein the upper and lower links are staggered relative to each other and are resiliently connected to each other so as to be expansible against the action of springs which are disposed within the links. The links of both layers also consist of shell-like casings and the upper links are open in the downward direction and the lower links are open in the upward direction. The springs are provided in the form of curved leaf springs and at least within the links of one layer. They engage on the one hand against the inside of the side walls of the links of one layer and on the other hand against certain parts which are connected to the links of the other layer, are slidable in a direction parallel to the side walls of the links of the first layer, and extend into these links through the opening thereof.

The above-mentioned objects of the invention are attained in an elastic link strap of the type as above described by connecting the links of one layer with the links of the other layer by means of connecting members of a zigzag-shaped cross section, each of which has a pair of parallel side wall portions which are staggered relative to each other and one of which is inserted into an upper link and the other into a lower link through the openings therein, so that these side Wall portions then extend substantially parallel to the side walls of the upper and lower links. The intermediate wall connecting these side wall portions and extending at right angles thereto is then disposed between the upper and lower links. The side walls of each connecting member are provided with slots extending inwardly from the ends thereof directly adjacent to the upper and lower surfaces of the intermediate wall. Both the upper and lower links are designed similar to the upper links of my previous construction as above described in that they both are provided with guide portions forming short tabs extending inwardly from their end walls at the level of the free edges of the side walls facing toward each other. These guide portions or tabs on each upper link and the adjacent lower link engage slidably into the mentioned slots of the connecting member and are guided therein for movement in the longitudinal direction of the strap. Each link of both layers also contains a pair of curved leaf springs, each of which engages on the one hand against the inside of one of the side walls of the respective link and on the other hand against the inside of the side wall of the connecting member which is inserted into this link.

By the addition of the connecting members according to the present invention it is possible to increase the extensibility of the strap considerably since it is determined not merely by the total of the compressibility of all of the leaf springs in the upper and lower links, but also by the total of the width of the intermediate portions of the connecting members which are disposed between the two layers of links. These connecting members are guided within both the upper and lower links in a similar manner as the extended side walls of the lower links of my previous strap construction as above described are guided within the upper links. Each of these extended side walls of the lower links is replaced in the strap design according to the present invention by one of the connecting members, the side walls of which are both slidable in the longitudinal direction of the strap with respect to the upper link as well as with respect to the adjacent lower link, and wherein each side wall of the connecting member may act upon a curved leaf spring in the upper link and one in the lower link until these springs are pressed fiat. The intermediate wall between the two side walls of each connecting member also fills out the gap which would otherwise appear between the adjacent links of both layers when the strap is being expanded. Thus, even when the strap is in the fully extended position, there are no unsightly gaps through which the skin of the wearer may be seen, by the strap will always present a closed appearance.

As already indicated, the structure of the link strap according to the invention is similar to the structure described at the beginning insofar as the guide portions also in this case consist of inwardly bent tabs which, however, are provided not only on the end walls of the upper links, but also of the lower links. The side walls of the upper links and in this case also of the lower links are likewise notched out at their ends to accommodate the inwardly bent tabs so that the outer surfaces thereof will be flush with the free edges of the side walls. Also similarly as in the strap as above described, at least some of the upper and/ or lower links may be provided with a cutout at or near one corner of the tab, and one of tongues which is formed by the slots in the side walls of one of the two connecting members which is inserted into a link having such a cutout is made shorter than the other tongues, that is, the tongue of that of the two adjacent connecting members in the link which moves away from this cutout when the strap is being expanded. The side wall of the connecting member having the shortened tongue may then be unhooked from the link when the connecting member is being turned to an oblique position opposite to the direction of expansion of the strap, whereby the shortened tongue will be moved in line with the cutout and may be slipped out of the cutout.

In order to insure that the leaf springs will not tip over when the strap is strongly bent, it has been found advisable to secure them to one of the side walls either of the connecting members or of the links by bending the edge portions of these side walls over the springs or by securing the springs at their center to one of these walls, for example, by a small bent-over tab or by spot welding. The spring may, however, also form an integral part of the side wall of the connecting member, in which case the respective side wall is made of a height greater by the width of the spring and is then cut longitudinally from both ends except for a small portion at the center where the extended portion of the side wall forming the spring is sharply bent over inwardly so that this central position will be substantially parallel to the side wall.

These and other objects, features, and advantages of the present invention will become further apparent from the following detailed description thereof, particularly when read with reference to the accompanying drawings, in which- FIGURE 1 shows a side view, partly in cross section, of a section of the elastic link strap according to the invention in the contracted position;

FIGURE 2 shows a side view of the same link strap section in the expanded position;

FIGURE 3 shows a plan view, partly cut open and in cross section, of a part of the strap in the contracted position;

FIGURE 4- shows a plan view, partly cut open and in cross section, of a part of the strap in the expanded position;

FIGURE 5 shows a perspective view of an upper link;

FIGURE 6 shows a perspective view of a lower link;

FIGURE 7 shows a perspective view of a leaf spring;

FIGURE 8 shows a perspective view of a connecting member; while FIGURE 9 shows a cross section of an upper link and a lower link held together by a connecting member with bent-over outer ends.

Referring to the drawings, it will be seen that the elastic link strap according to the invention consists of only three different kinds of parts, namely, the upper links 10 and the lower links 20 which are both of the same construction, the leaf springs 30, and the connecting members 40. Each upper link 10 forms a small shell which is open in the downward direction, while each lower link 20 forms a similar shell which is open in the upward direction. Each link is made of a single stamped piece which is bent to form the upper wall 11 or the lower wall 21, respectively, the side walls 12 or 22, respectively, and the end walls 13 or 23, respectively, which form a part of the longitudinal sides of the strap. The side walls 12 and 22 are provided at the ends of their free edges with cutouts 14 and 24, respectively, into which tablike extensions 15 and 25, respectively, are bent so that the outer surfaces of these tabs, that is, the lower surfaces of tabs 15 of the upper links, as shown in FIGURE 5, and the upper surfaces of tabs 25 of the lower links, as shown in FIGURE 6, are disposed within the same plane as the free edges of side walls 12 or 22, respectively. These tabs 15 and 25 are, however, not bent inwardly until the strap is being assembled. The connecting member 4-0 is of a zigzagshaped cross section consisting of a pair of parallel side walls 41 and 42 which are offset relative to each other and extend in opposite directions from and at a right angle to the intermediate connecting wall 43. Side walls 41 and 42 and the intermediate wall 43, as seen in a direction transverse to the longitudinal direction of the strap, have a length substantially equal to the inner length of the upper and lower links 10 and 20 between the opposite end walls 13 and 23 thereof. The side walls 41 and 42 of the connecting members 40 are provided with slots 44 which extend inwardly from the outer ends thereof directly adjacent to the upper and lower surfaces of the intermediate wall 43. By these slots 44, tongues 45, 45' are formed at each end of side walls 41 and 42. The side walls 41 of two connecting members 40 which are disposed in an inverse relation to each other are inserted into one upper link with a leaf spring 30 being interposed between each of these side walls 41 and the inner surfaces of the side walls 12 of this link 10, whereupon the tabs 15 on end walls 13 are bent inwardly into the slots 44. The side walls 42 of these two connecting members are then inserted into two adjacent lower links 20, likewise with leaf springs 30 being interposed between the inner surfaces of side walls 22 of links and of side walls 42 of the two connecting members 40. After a further connecting member 40 with a spring 30 has been inserted at the other side of each of the two lower links 20, the outwardly bent tabs are then likewise bent toward the inside into slots 44. The connecting members 40, each of which connects one upper link with one lower link, cooperate with the tabs 15 and 25 so as to guide the links in both layers relative to each other. When the strap is being expanded, the connecting members 40 slide in the longitudinal direction of the strap against the action of the interposed leaf springs which they compress until, in the fully expanded position of the strap, these springs are pressed flat between the side walls 41 and 42 of the connecting members and the side walls 12 and 22 of the upper and lower links, respectively. It will be evident especially from an examination of FIGURE 2 that the extensibility of the link strap has been considerably increased in this manner over that of the strap according to my previous application as first described herein.

The outer ends 31 of leaf springs are provided with cutouts 32 of a depth and width in accordance with the thickness and width of the tabs 15 or 25. Thus, the springs will be guided within the links along the tabs and will not tip over when the strap is being bent. Leaf springs 30 may also be centrally secured to the side walls 41 or 42, as indicated in FIGURE 8, for example, by being spot-welded to these side walls as shown at 50. If the connecting members are made of a spring material, the springs may also be made integral with the connecting members. The side walls 41 and 42 are then made of a greater height and the part of each side wall which is subsequently intended to serve as a spring 30 is cut off except for a small central web and then bent sharply inwardly about the cutting edge so that the central portion of the spring 30 will be parallel and substantially in engagement with the central portion of the side wall 41 or 42. After the arms of the springs are then bent away from the side walls 42 and 42 to give the springs the necessary curvature to have the desired resilience, the leaf spring will form an integral part of the connecting member 40 and be in the position as indicated in FIG- URE 8 in dotted lines. FIGURE 9 illustrates a further modification of holding the leaf springs 30 in the proper position within the links. The side walls 41a and 42a of the connecting members 40 are provided with bentover edge portions 47 which engage the two springs 30 along one longitudinal edge thereof, while the side walls 12a and 22a of the links 10 and 2.0 also have inwardly bent edge portions 17 and 27, respectively, which engage the two springs along the other longitudinal edge thereof.

In order to permit the links to be unhooked from each other at any desired part of the strap or at least at certain parts thereof, the guide tab 15 or 25 of a particular link may be provided near one corner with a cutout 26, and the corresponding tongue 45 on a side wall 42 of that of the two connecting members 40 engaging into the mentioned link which moves in a direction away from, rather than toward the cutout 26 when the strap is being expanded is shortened by a certain length as indicated by the hatched part 46 in FIGURE 8. For unhooking the connecting member 40 with the shortened tongue 45 from the link with the cutout 26 therein, it is only necessary first to expand the strap so that leaf springs 30 will be flattened completely between side walls 12 and 41 of the upper links and connecting members 40 and between side walls 22 and 42 of the lower links and the connecting members, and then, while holding the adjacent links in such expanded position, to turn one of the connecting members which has such a shortened tongue 45 to an oblique position opposite to the direction of expansion of the strap so that the end of the side wall of the connecting member which has the shortened tongue 45' will be pushed and placed in line with the cutout 26. The shortened tongue 45' will be pushed back and placed in line with the cutout 26. The shortened tongue 45' may then be slipped through cutout 26 and the other full tongue 45 on the same side wall of the connecting member may then also be unhooked from the opposite tab 15 or the respective link. Depending upon the number of links provided with such cutouts 26 and the number of connecting members provided with such shortened tongues 45, it will be possible to shorten the strap at one point or at various points and it will even be possible to unhook all of the links and connecting members.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. An elastic link strap comprising a plurality of upper and lower links extending transversely to the longitudinal direction of the strap and superimposed upon each other so as to form two layers, the upper links being staggered relative to the adjacent lower links in the longitudinal direction of the strap, each of said links forming a hollow shell-like casing, each of said upper links having an upper wall, side walls, and end walls and being open in the downward direction, each of said lower links having a bottom wall, side walls, and end walls and being open in the upward direction, a plurality of connecting members, each consisting of two side walls and an intermediate wall secured to said side walls and extending at right angles thereto and interposed between the links of the two layers, said side walls of each connecting member projecting into one upper link and an adjacent lower link through the respective openings thereof and extending parallel and offset to each other in opposite directions from said intermediate wall, said side walls of each connecting member having slots therein extending inwardly from the ends thereof directly adjacent to the upper and lower surfaces of said intermediate wall, each of said links of both layers having guide portions thereon within the plane of the free edges of said side walls thereof adjacent to the opening of said link, said guide portions being slidably guided within said slots, and at least two curved leaf springs disposed within each link of both layers and each interposed between a respective one of said side walls of said connecting member and an adjacent side wall of a respective one of said links of said layers so that said springs will be pressed flat when said strap is being expanded or bent.

2. An elastic link strap as defined in claim 1, wherein said guide portions on each of said upper and lower links form tabs bent inwardly from the end walls of said links, the ends of said side Walls of each of said links being notched out to accommodate said tabs so that said tabs are disposed within the plane of the free edges of said lastmentioned side walls adjacent to the opening of the respective link.

3. An elastic link strap as defined in claim 1, wherein said guide portion on at least some of said links is provided with a cutout near one corner thereof, each slotted end portion of said side walls of each of said connecting members forming a tongue, said tongue on one of the two connecting members inserted into said link having said cutout being shorter than the other tongues, said shortened tongue moving away from saidtcutout when said strap is being expanded, so as to permit said side wall of said one connecting member having said shortened tongue to be unhooked from said link having said cutout when said one connecting member is being turned to an oblique position opposite to the direction of expansion of the strap whereby said shortened tongue will be moved in line with said cutout and may then be slipped out of said cutout.

4. An elastic link strap as defined in claim 1, further comprising a bent-over edge portion on each side wall of each of said links for guiding one of said springs to prevent the same from tipping over when said strap is being bent.

5. An elastic link strap as defined in claim 1, further comprising a bent-over edge portion on each side wall of each of said connecting members and a bent-over edge portion on each side wall of each of said links, said bent-over edge portions on one of said side walls of said connecting member and on one of said side walls of said link extending substantially parallel and in a spaced relation in opposite directions to each other to engage one of said springs at opposite sides thereof and to guide said 8 spring to prevent it from tipping over when said strap is being bent.

6. An elastic link strap as defined in claim 1, further comprising means for securing each of said springs substantially centrally thereof to one of said side walls of each of said connecting members.

7. An elastic link strap as defined in claim 1, further comprising means for securing each of said springs substantially centrally thereof to one of said side walls of each of said links.

References Cited in the file of this patent UNITED STATES PATENTS 1,089,931 Loog Mar. 10, 1914 1,132,099 King Mar. 16, 1915 1,461,203 Bauer et al. July 10, 1923 2,513,288 Cowan July 4, 1950 FOREIGN PATENTS 1,205 Great Britain 1914 166,288 Great Britain July 15, 1921 623,391 Great Britain May 17, 1949 802,945 Great Britain Oct. 15, 1958 1,161,288 France Mar. 17, 1958 538,417 Italy Jan. 25, 1956 72,537 Switzerland June 2, 1916 

1. AN ELASTIC LINK STRAP COMPRISING A PLURALITY OF UPPER AND LOWER LINKS EXTENDING TRANSVERSELY TO THE LONGITUDINAL DIRECTION OF THE STRAP AND SUPERIMPOSED UPON EACH OTHER SO AS TO FORM TWO LAYERS, THE UPPER LINKS BEING STAGGERED RELATIVE TO THE ADJACENT LOWER LINKS IN THE LONGITUDINAL DIRECTION OF THE STRAP, EACH OF SAID LINKS FORMING A HOLLOW SHELL-LIKE CASING, EACH OF SAID UPPER LINKS HAVING AN UPPER WALL, SIDE WALLS, AND END WALLS AND BEING OPEN IN THE DOWNWARD DIRECTION, EACH OF SAID LOWER LINKS HAVING A BOTTOM WALL, SIDE WALLS, AND END WALLS AND BEING OPEN IN THE UPWARD DIRECTION, A PLURALITY OF CONNECTING MEMBERS, EACH CONSISTING OF TWO SIDE WALLS AND AN INTERMEDIATE WALL SECURED TO SAID SIDE WALLS AND EXTENDING AT RIGHT ANGLES THERETO AND INTERPOSED BETWEEN THE LINKS OF THE TWO LAYERS, SAID SIDE WALLS OF EACH CONNECTING MEMBER PROJECTING INTO ONE UPPER LINK AND AN ADJACENT LOWER LINK THROUGH THE RESPECTIVE OPENINGS THEREOF AND EXTENDING PARALLEL AND OFFSET TO EACH OTHER IN OPPOSITE DIRECTIONS FROM SAID INTERMEDIATE WALL, SAID SIDE WALLS OF EACH CONNECTING MEMBER HAVING SLOTS THEREIN EXTENDING INWARDLY FROM THE ENDS THEREOF DIRECTLY ADJACENT TO THE UPPER AND LOWER SURFACES OF SAID INTERMEDIATE WALL, EACH OF SAID LINKS OF BOTH LAYERS HAVING GUIDE PORTIONS THEREON WITHIN THE PLANE OF THE FREE EDGES OF SAID SIDE WALLS THEREOF ADJACENT TO THE OPENING OF SAID LINK, SAID GUIDE PORTIONS BEING SLIDABLY GUIDED WITHIN SAID SLOTS, AND AT LEAST TWO CURVED LEAF SPRINGS DISPOSED WITHIN EACH LINK OF BOTH LAYERS AND EACH INTERPOSED BETWEEN A RESPECTIVE ONE OF SAID SIDE WALLS OF SAID CONNECTING MEMBER AND AN ADJACENT SIDE WALL OF A RESPECTIVE ONE OF SAID LINKS OF SAID LAYERS SO THAT SAID SPRINGS WILL BE PRESSED FLAT WHEN SAID STRAP IS BEING EXPANDED OR BENT. 